A simple repair method for GFRP delaminati on using ultraviolet- curable resin
Limin Baoa*, Takuya Okazawaa, Anchang Xub and Jian Shic
aFaculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda-shi, Nagano Prefecture 386-8567, Japan; bCollege of Textile Science and Engineering, Wuhan Textile University, 1st FangZhi Road, Wuhan 430073, P.R. China; cFaculty of Systems Science and Technology, Akita Prefectural University, 84-4 Ebinokuchi Aza, Tsuchiya, Yurihonjo-shi, Akita
Prefecture, Japan
Abstract
Fiber-reinforced plastic (FRP) composites are widely used in engineering because of their high strength and light weight in comparison to monolithic metal alloys. They are mostly used in laminate form and are stronger within layers than between layers,
making them prone to cracking and peeling. This type of structural degradation can be dangerous during operation. For this reason, research on FRP composites with the ability to self-repair has attracted much attention. In this study, we developed a
new method to repair glass fiber-reinforced plastic (GFRP) composites by using ultraviolet-(UV) cured resin. As GFRP composites are UV transmissive, the repair process can be carried out externally by exposing the damaged part to UV light.
The transmittance of EP GFRP is about 40%. Holes were pre-drilled with wires in order to facilitate the injection of UV resin between the layers of the composite, and this process was accomplished without degrading the mechanical properties of the
material. A double cantilever beam (DCB) test was performed on the GFRP composite to induce interlaminar fracturing. UV-curable resin was then injected between the layers of the composite through a series of pre-drilled holes. Following this
repair, the DCB test was performed again to evaluate the repair rate. A compressive after impact (CAI) test was also performed on the GFRP composite to induce delamination. Compressive strength before and after the repair was also evaluated.
Keywords: GFRP; repair method; ultraviolet-curable resin; DCB test; CAI test
Effect of matrix ductility on fatigue strength of unidirectional jute spun yarns impregnated with biodegradable plastics
Hideaki Katog ia*, Yoshinobu Shimamurab, Keiichiro Tohgob, Tomoyuki Fujiib and Kenichi Takemuraa
aDepartment of Mechanical Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686, Japan; bDepartment of Mechanical Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan
Abstract
Natural fiber-reinforced composites are carbon-neutral materials that are anticipated for use as an alternative to glass fiber-reinforced plastics. This study investigated the effects of matrix ductility on the fatigue strength of unidirectional jute spun yarns
impregnated with biodegradable plastics. Polylactic acid (PLA) and polybutylene succinate (PBS) were used for the matrix. PLA is brittle, but it is widely used as a matrix of green composites. Because PBS has much higher ductility than that of PLA, it can be expected to have higher fatigue strength when subjected to the same strain amplitude as PLA. Fatigue tests were conducted with maximum stress set to 40–90% of the tensile strength. The stress ratio was set as 0.1. Results show that the matrix ductility strongly affects the fatigue strength and the fatigue mechanism of the composite. A matrix with better ductility was effective to improve fatigue strength.
Keywords: jute spun yarn; unidirectional reinforcement; fatigue; biodegradable plastics; PLA; PBS
Exper imental study of size effect on quasi-static strengths for short gla ss fi bre-reinforced plastics
Takahik o Sa wadaa* and Takayuki Kusakab
aCenter for Technology Innovation – Mechanical Engineering, Research & Development Group, Hitachi, Ltd., Hitachinaka, Japan; bDepartment of Mechanical Engineering, Ritsumeikan University, Kusatsu, Japan
Abstract
The present paper examines size effect on the strength of short glass fibre-reinforced phenolic resin (SGP) composites made by press moulding with different loading modes and specimen shapes. Three- and four-point flexural tests and tension–torsion
combined tests were conducted at room temperature in order to evaluate the influence of Vf and loading mode on fracture strength. The obtained uniaxial strength data were analysed using the Weibull statistical theory. The relationship between
fracture strength and effective volume was investigated based on the Weibull statistical theory and agreed well with the effective volume theory (EVT), regardless of specimen size, dimensions or loading mode. The experimental results revealed that
the tension–torsion multiaxial SGP strength was in agreement with the Tsai–Hill failure criterion. The EVT was also applied to the Tsai–Hill failure criterion to consider the size effect, and the validity of the proposed method was confirmed experimentally.
Keywords: short glass fibre-reinforced plastics; size effects; strength
Improved adhesion betwee n nickel–titanium SMA and polymer matrix via acid treatment and nano-silica particles coating
Bi n Yanga*, Yongchao Zhangb, Fu-Zhen Xuana, Biao Xiaoa, Liang Heb and Yang Gaoa
aSchool of Mechanical and Power Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai, 200237, China; bCollege of Aerospace and Civil Engineering, Harbin Engineering University, Harbin, China
Abstract
Shape memory alloy (SMA) composites are the desirable candidate for smart materials that used in intelligent structures. However, the overall mechanical performance of SMA composites depends immensely on the quality of the interaction between
SMA and polymer matrix. Therefore, it is necessary to find out an approach to enhance the interfacial property of this composite. In this paper, we modified nickel–titanium SMA wire with nano-silica particles before and after acid treatment. The modification effect on the interfacial strength between SMA and epoxy resin was evaluated. Contact angle analysis, scanning electron microscopy (SEM) observation, and single fiber pull-out test were carried out. The bonding characteristics between modified wire and liquid/cured resin were investigated. We then embedded SMA wire into woven glass fabric/epoxy composite laminates, and manufactured this hybrid composites via vacuum assisted resin transfer molding processing. Three-point-bending test of the hybrid composites was performed to validate the modification effect. Fiber pull-out experiment demonstrates that the interfacial shear strength increases by 6.48% by nano-silica particles coating, while it increases by 52.21% after 8 h acid treatment and nano-silica particles coating simultaneously. For hybrid composites, flexural strength of the two specimens increases by 19.8 and
48.2%, respectively. In SEM observation, we observed large debonding region in unmodified composites, while interfacial adhesion between modified wire and epoxy keeps strong after flexural damage.
Keywords: shape memory alloy; surface modification; interfacial adhesion strength; SMA hybrid composites; fiber pull-out test
Novel optimization method of single square FSS impinged and cascaded radar absorbing composites
Ravi Panwa ra, Dae-Sung Sonb and Jung-Ryul Leeb*
aIndian Institute of Information Technology, Design & Manufacturing, Jabalpur, Madhya Pradesh, India; bOpto-Electro-Structural Lab, Korea Advanced Institute of Science & Technology (KAIST), Daejeon, South Korea
Abstract
It is well known that radar absorbing potentiality of existing magneto-dielectric composites can be significantly enhanced by the application of frequency selective surface (FSS) and cascaded electromagnetic (EM) structures. But the optimization of such complex EM structures and validation of the adopted optimization strategy is still a very challenging task for the researchers. Therefore, in this study, an effective effort has been made for the optimization and the corresponding validation for Single Square FSS (SS-FSS) impinged and cascaded radar wave absorbers using advanced computational EM software’s like FEldberechnung fur Korper mit beliebiger Oberflache – a German acronym (FEKO) and high frequency structure simulator (HFSS). In addition, a critical analysis of dielectric constant (ε′) has been carried out to select the best combination of composites for the development of effi- cient radar wave absorbers. A comparison between optimized and simulated results have been carried out to examine the effect of advanced EM approaches over reflection loss (RL) characteristics of composite radar absorbing materials (CRAMs). A
rapid change in radar absorption properties of composites has been observed after the application of SSFSS and cascading. A SS-FSS impinged composite has been found to provide a wide absorption bandwidth of 3.6 GHz at X-band. A cascaded absorber having layer thickness 1.8 mm provides a peak RL of −42.6 dB at 10.6 GHz with an absorption bandwidth of 2.5 GHz. The strong agreement between mathematical model, HFSS and FEKO results clearly reflects the efficiency of adopted approach for distinct practical EM applications.
Keywords: Radar wave absorber; composite; stealth; frequency selective surface
Optimal fiber distribution for tensile properties of injection molded composite
Dong-Joo Lee*
School of Mechanical Engineering, Yeungnam University, Gyungsan 712-749, South Korea
Abstract
The survival rate of a composite is the residual fiber length divided by the initial fiber length, and it decreases with the initial fiber length and fiber volume content ( Vf) during injection molding processes. The degree of damage is higher for carbon fiber than for glass fiber, and the survival rate increases with a hyperbolic tangent relationship as the nozzle diameter increases. Higher survival rate corresponds to a stronger material. Five different lengths of fiber with 29 different size fibers were selected based on the distribution and shape of residual fiber in experimental works. These were examined to study the effects of fiber distribution on the tensile properties of a short-fiber reinforced composite (SFRC). Compared with the experimental results, the modulus predicted using the Halpin-Tsai relation shows reasonable agreement with the prediction obtained using the residual fiber length instead of the initial fiber length. It was found that the tensile modulus and strength generally differ by a factor of up to 3.2, depending on the fiber distribution patterns with Vf = 30%, and the trend is more significant as the fiber aspect ratio increases. The interactions between the fiber and matrix and the staggered-type distribution are the most important factors in the reinforcement of the SFRC. With the same combination of short fiber length, an optimized fiber distribution pattern is suggested.
Keywords: fiber aspect ratio; damage during injection molding; fiber distribution; tensile strength and modulus; prediction
Rayleigh waves at the boundary surface of modified couple stress generalized thermoelastic with mass diffusion
Rajnees h Kumara*, S.M. Abo-Dahabb,c and Shaloo Devid
aDepartment of Mathematics, Kurukshetra University, Kurukshetra, India; bMathematics Department, Faculty of Science, Taif University, Taif, Saudi Arabia; cMathematics Department, Faculty of Science, SVU, Qena, Egypt; dDepartment of Mathematics & Statistics, Himachal Pradesh University Shimla, Shimla, India
Abstract
In this problem, we have studied propagation of Rayleigh waves in an homogeneous isotropic modified couple stress generalized thermoelastic with mass diffusion solid half space in the context of Lord–Shulman (L-S), Green–Lindsay (G-L) theories of
thermoelasticity. Secular equations are derived mathematically by using appropriate boundary conditions. The values of determinant of secular equation, Rayleigh wave velocity and attenuation coefficient with respect to angular velocity for different values of wave number and relaxation times in the absence and presence of mass diffusion, are computed numerically. The numerical simulated results are depicted graphically for copper material.
Keywords: Rayleigh waves; modified couple stress theory; thermoelastic diffusion; Rayleigh wave velocity; attenuation coefficient
Energ y absor ption behaviour of braided basalt composite tube
M. Nazr ul Roslana,b , M. Yazid Yahyab*, Z. Ahmadb and A.R. Azrin Hania
aAdvanced Technology Centre, Faculty of Engineering Technology, Universiti Tun Hussein Onn Malaysia, 84600 Batu Pahat, Johor, Malaysia; bCentre for Composite, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
Abstract
Braided composite had been proven to have a great potential as energy absorber. However, the past studies done were limited to synthetic fibre as the reinforcement composite. In this study, we focused on a natural fibre, namely basalt, as the reinforcement material. The effects of braid thickness, braid angle and braid tow density of the basalt composite tube subjected to quasi-static crushing response were investigated. Crushing failure mode had been observed in comparing those braid parametric effects. Moreover, the analysis of variance was used to analyse the main and interaction effects subjected to specific energy absorption (SEA) response for the test. Three crushing modes had been observed. The splayed and diamond shape of progressive folding were reported for the braid angles of ±30° and ±45°, respectively, and fibre micro-cracking mode effects for the ±60° braid angle. Furthermore, SEA increased with the decrease of braid angle and increase of diameter-to-thickness ratio. On the other hand, the highest braid angle demonstrated the lowest crush efficiency and poor triggering crushing progression.
Keywords: basalt fibre; braided tube; crushing
Failure behavior of quasi-isotropic carbon fi ber-reinforced polyamid e composites under tension
Mazl ina Mohd Tahira*, Wen-Xue Wangb and Terutake Matsubarab
aDepartment of Aeronautics and Astronautics, Engineering School, Kyushu University, Motooka Nishi-ku, Fukuoka 819-0395, Japan; bResearch Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan
Abstract
In this paper, the microscopic failure behavior of quasi-isotropic carbon fiberreinforced polyamide-6 (CF/PA6) laminates under tension was investigated experimentally. Laminates of two layups, namely [45°/0°/−45°/ 90°]s and [45°/0°/−45°/90°]2s, were made from CF/PA6 tapes of two different manufacturers and then subjected to tensile testing. Crack initiation and progression on the polished free edge of specimens were examined using optical microscopy, under several load levels. Crack growth behavior through the specimen width was also traced by observing the crack configurations in different sections in the specimen width direction. The effects of the spatial distribution of fiber on the microscopic damage events were elucidated. The difference in failure behavior between the present CF/PA6 laminates and conventional thermosetting CF/Epoxy laminate is discussed.
Keywords: thermoplastic composites; fiber distribution; tensile test; damage behavior
Identification of preferred combinati on of factors in manufacturin g bioepoxy/clay nanocomposites
H. Salama,b, Y. Donga* , I. J. Daviesa and A. Pramanika
aSchool of Civil and Mechanical Engineering, Curtin University, Perth, WA 6845, Australia; bDepartment of Mechanical Engineering Education, Indonesia University of Education, Bandung 40153, West Java, Indonesia
Abstract
The current study aims to identify the preferred combination of factors for manufacturing bioepoxy/clay nanocomposites based on epoxidised soybean oil (ESO), including material formulation and manufacturing parameters for maximising tensile
strengths of nanocomposites according to Taguchi design of experiments (DoEs). A Taguchi mixed-level DoEs with an L16 orthogonal array was selected. The response was set to achieve the maximum tensile strengths of nanocomposites with a preferred combination of factors determined by the Pareto analysis of variance (ANOVA). The associated results revealed that the ESO content was found to be the most significant factor with a contribution percentage of 66.63% amongst nine factors investigated. This result was followed by two less significant factors, namely mechanical mixing speed and clay content with contribution percentages of 19.09 and 7.01%, respectively. However, other factors of clay type, curing agent type, mechanical mixing temperature and time, as well as sonication frequency and time, were categorised as non-significant factors from the manufacturing and economical point of view. A confirmation test was conducted based on the preferred combination of factors showing good agreement with statistically predicted results.
Keywords: bioepoxy/clay nanocomposites; Taguchi design of experiments (DoEs); mechanical properties; morphological structures
Layer-by-layer assembled graphene oxide/polydiallydimethylammonium chloride composites for hydrogen gas barrier application
Song-M oo Leea, Hun Jeong*b, Nam Hoon Kima, Hong-Gun Kimb and Joong Hee Lee*a,c
aAdvanced Materials Institute of BIN Convergence Technology (BK21 plus Global) & Dept. of BIN Convergence Technology, Chonbuk National University, Jeonju, Jeonbuk 54896, Republic of Korea; b Institute of Carbon Technology, Jeonju University, Jeonju, Jeonbuk 55069, Republic of Korea; cCenter for Carbon Composites Materials, Department of Polymer & Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk 54896, Republic of Korea
Abstract
Poly(diallyldimethylammoium chloride) (PDDA)/acid or base modified graphene oxide (MGO) composite (PDDA/MGO)-based gas barrier films were prepared by layer-by-layer (LBL) assembly method on polyethylene terephthalate (PET) substrate using a spray coating assisted deposition. The effect of pH on the hydrogen gas permeability (H2GP) values of the different MGO-based films was investigated to determine the optimum pH value of the MGO solution for the preparation of PDDA/MGO-based LBL assembly. Accordingly, the different numbers of bilayers based LBL-assembled films were prepared using alternate deposition of PDDA and MGO solutions and the H2GP values were measured for those assemblies. The films were characterized by XRD, FT-IR, and Raman spectroscopy analyses. The morphology of the LBL-assembled film was observed by cross-sectional field emission scanning electron microscopy which confirms densely packed layered structure. The H2GP of six bilayers PDDA/MGO composite film is 5.7 cc/m2 ⋅d⋅atm, which is much lower than that of pure PET substrate (170.7 cc/m2 ⋅d⋅atm), indicating 96.7% decrease in H2GP. This result suggests that the PDDA/MGO composite film could be used as a potential candidate to fabricate hydrogen gas barrier coating material.
Keywords: hydrogen gas barrier; graphene oxide; layer-by-layer assembly; composites; poly(diallyldimethylammoium chloride)
Specimen size effects on fracture behaviour of SiC/SiC tubes during circumferential tensile test
Ju-Hyeon Yu a, Hirotatsu Kishimotob, Naofumi Nakazatob, Joon-Soo Parkb
and Akira Kohyamab
aGraduate School of Engineering, Muroran Institute of Technology, Muroran, Japan; b Organization of Advanced Sustainability Initiative for Energy System/Materials, Muroran Institute of Technology, Muroran, Japan
Abstract
SiC fiber-reinforced SiC matrix (SiC/SiC) composites are expected as a high-temperature structural material for the application of aerospace and nuclear energy system due to their high-temperature stability, reduced-activation property, and excellent irradiation resistance. It was investigated the size effects of test specimen on the fracture behaviour and apparent strength of SiC/SiC tubes in order to minimize the size of test specimen, as well as to develop circumferential tensile test method for SiC/SiC fuel cladding of
nuclear reactor. The tube specimens with a narrow width (less than 5 mm) represented the stable value of apparent strength. In case of wide width (>5 mm), the apparent strength of test specimen decreased with the increase in specimen width. It was observed that the fracture of the test specimen with wide width was initiated from the sides of test specimen due to the local contact between loading pin and the test specimen. It is required to use the material with high modulus as a loading pin material in order to avoid the stress concentration caused by local contact.
Keywords: Silicon carbide; SiC/SiC composites; size effects; fracture behaviour; circumferential tensile test
